1. Field of the Invention
The present invention relates to an image processing system for displaying desired image information, such as characters, graphics and pictures, on a screen of a display unit, e.g., CRT (Cathode Ray Tube), monitor or the like.
More specifically, the present invention relates to an image processing system which enables image information written into a bit-map memory having a new specification to be easily sent from a new type of display adapter to a display unit, in the case where such a new adapter is provided as hardware.
Furthermore, the present invention relates to an image processing system which enables the image information that has been displayed on the screen to be continuously displayed with a sufficient accuracy without necessity for modifying and exchanging the specifications of host units, even in the case where the resolution of the image information on the screen is changed.
2. Description of the Related Art
In recent years, a number of image processing systems having bit-map memories, have been produced in order to display various image information on a display unit, such as a CRT. The image information includes characters, graphics and pictures. With respect to display hardware represented by the size of bit-map memories of the respective image processing systems, there are many values of memory capacity. For example, one system has a smaller memory capacity such that only a monochrome display can be produced. Another system has a relatively large memory capacity such that 256 colors can be produced. Still another system has a remarkably large memory capacity such that full-color display utilizing as many as 160,000 colors can be produced.
Further, with respect to hardware and software for display of the image processing systems, there are many levels of functions which these systems can perform. For example, one system contains a bit-map memory only in principle and has relatively low cost. Another system has an additional function referred to as a graphics accelerator, which enables the drawing process to be executed at high speed, as well as a simple function utilizing a bit-map memory only.
In many cases, such image processing systems are provided for users in the form of adapters which are to be connected to an I/O (Input/Output) bus, e.g., the VME (Versa Module European) bus. When various image information (such as characters, graphics and pictures) is to be written into the bit-map memory of the image processing system, it is necessary for such image information to be processed by the above-mentioned image processing system, taking into consideration the type of the bit-map memory used by units concerned with the drawing process within the given system.
Further, in the case where the function of the drawing process, e.g., the character display process, is provided by the image processing system in the form of a standard specification, the system is required to execute such a drawing process assuredly for any kind of adapter which will be realized in the future. Namely, even when various kinds of bit-map cards {for example, an adapter including an adapter ROM (Read Only Memory)}, each of which has a hardware specification different from the standard specification, is provided, it is necessary for the given system to take in and utilize the drawing information contained in the above-mentioned bit-map cards in order to easily extend the display function.
Further, with respect to resolutions of the image information in the bit-map memories, a number of image processing systems, which extend from the fields of personal computers through workstations and include various kinds of resolutions, are currently provided. In many cases, software working on these systems is operative under the condition that the above-mentioned software is conscious of these resolutions. If all these software packages, related with the respective resolutions, are to be utilized effectively in the given image processing system, it is often necessary for such a system to have a function in which the changeover process of these resolutions can be executed, e.g., by utilizing another kind of software that supports a plurality of resolutions and allows them to be operative.
Further, in such a system where a plurality of resolutions can be supported, the system is required to accurately display the image information that has been displayed on the screen before changing the resolution, even when the resolution of the image information on the screen has been changed while characters, etc., are being displayed on the screen. After the resolution has been changed, the system is also required to continue the same drawing process as that executed heretofore.
Here, some operations of image processing systems according to the prior art will be explained more specifically.
In the case where a new type of adapter is fabricated (i.e., in the case where the specification of hardware of the system is to be changed by adopting such a new type of adapter), it becomes naturally necessary to change the specification of software of the system simultaneously. Therefore, every time a new type of adapter is provided for a system, the specifications of the hardware and the software thereof have to be changed. To avoid such troublesome work, in the systems according to the prior art utilized in the fields of personal computers, workstations and the like, the kind of available bit-map memories in the adapters, which can be connected to the I/O bus, is likely to be limited to a certain extent. Further, when a given system is required to support a new available bit-map memory, a process of modifying the drawing information stored in ROM within a mainframe of the system is executed, or otherwise another process of supporting the new bit-map memory by a newly developed model (software) is executed.
To be more specific, the portion having the function of drawing process within a mainframe of the system, which the system provides mainly as software and which constitutes the main part of host image processing units of the system, is modified in a manner such that the software is conscious of the specification of hardware in a new bit-map memory card. In this way, the above-mentioned portion executes a drawing process and a changeover process of resolutions of the image information. Furthermore, when another new bit-map memory card is to be connected to the I/O bus, the software of the above-mentioned portion within a mainframe is sometimes replaced with a newly developed software in a region other than the mainframe.
Here, to allow some problems regarding such conventional image processing systems to be understood more clearly, a concrete configuration of bit-map memory for displaying image information on a screen will be described with reference to the related drawings of FIGS. 1A and 1B. In this case, an example in which characters are displayed on the screen will be explained representatively. Further, it should be noted that the whole bit-map memory having the memory capacity of 2048 bits.times.2048 bits is contained in the memory area of the system.
FIGS. 1A-1 and 1A-2 are diagrams for explaining a changeover process of resolutions of characters; and FIG. 1B is a diagram for explaining a drawing process of characters on a screen.
First, as shown in FIG. 1A-1, a portion of the whole memory area (2048 bits.times.2048 bits), which corresponds to a bit-map area having a resolution of 1280 bits.times.1024 bits, is assumed to be displayed on a screen of a CRT.
Next, as shown in FIG. 1A-2, it is assumed that a different bit-map memory card is provided, and that the resolution of characters in the same bit-map area has to be changed to the value of 1024 bits.times.768 bits.
The following Table I shows the definition of reference numerals in FIGS. 1A-1 and 1A-2.
TABLE I ______________________________________ REFERENCE DESCRIPTION NUMERAL ______________________________________ HEAD CO-ORDINATE OF CHARACTER 100 DISPLAY AREA BIT-MAP AREA 102 MEMORY AREA 104 CHARACTER DISPLAY AREA 106 SPACE BETWEEN THE LINES 108 ______________________________________
In this configuration of bit-map memory, each of memory addresses in the memory area is located in such a drawing process as shown in FIGS. 1B-1, 1B-2 and 1B-3. In FIGS. 1B-1, 1B-2 and 1B-3, reference numeral 110 corresponds to address 0, reference numeral 112 corresponds to address 1, reference numeral 113 corresponds to address N+1, and reference numeral 114 corresponds to address N. In this case, the memory addresses are sequentially located on the first line toward the right direction, such as address 0, address 1 and so forth. After the memory address has become address N on the rightmost position, i.e., the last column position, on the first line, address N+1 corresponding to the next memory address is moved to the leftmost position, i.e., the first column position, on the second line. Namely, the head address on the second line is equivalent to the memory address next to the last address on the first line. In this way, all the memory addresses are located in the whole memory area at every line.
Returning to FIG. 1A, even when the resolution is changed as described above, it is generally required to continue to display the same characters as those displayed before the change of resolution on the screen. To meet this requirement, drawing information, e.g., a head co-ordinate of character display area within the bit-map area, a space between the adjoining lines, etc., has to be defined as the drawing information dependent on resolution. In the portion having a function of drawing process, e.g., a function of character display process, within the mainframe of the system, memory addresses (which are necessary to display desired characters) are determined in accordance with the above-mentioned drawing information dependent on resolution.
However, in such a address-mapping method as described with reference to FIGS. 1B-1, 1B-2 and 1B-3, every time the resolution of characters is changed, the value of the head co-ordinate of character display area and the value of the space between the adjoining lines are likely to be changed. Therefore, memory addresses utilized for displaying desired characters are also changed. Even in this case, it is necessary to accurately display the same characters on the screen, regardless of the changeover process of resolutions.
As described above, in the case where a new bit-map memory is to be supported, the image processing system in the prior art is likely to deal with the new bit-map memory by executing a modification or exchange of programs stored in advance in the ROM in the mainframe, which is constructed as a part of the hardware. Alternatively, the system is likely to take measures by executing a modification or replacement of the portion having a function of drawing process, which is included in the mainframe and mainly realized as the software. In other words, either the hardware or software of host processing units of the system has to be modified or exchanged with another one, every time the new bit-map memory is provided. Therefore, a problem occurs that a troublesome work becomes necessary at the time of such a modification or exchange.
Further, in the case where the resolution is to be changed, it is difficult to always display the same characters as displayed previously on the screen with an accuracy, after the changeover process of resolutions has been executed. Therefore, another problem occurs that the form of each of the characters, etc., such as the position of the character to be displayed, the character size, and the space between the adjoining lines, is likely to be distorted.